The present invention is directed to a refrigerant gas leak detector for detecting the presence and location of leaks of refrigerant gases such as halogen used in refrigeration systems.
A refrigerant gas leak detector is disclosed in U.S. Pat. No. 3,742,475 to Liebermann. In that detector, a high voltage is applied across a pair of electrodes disposed in an atmosphere to generate a continuous corona across the electrodes. The continuous corona causes a corona current to pass across the electrodes. When exposed to varying concentrations of gaseous impurities such as halogens, the magnitude of the corona current changes. The Liebermann detector detects the presence of gaseous impurities based on changes in corona current magnitude. The detection circuit includes two sensitivity settings for manually changing the sensitivity of the detector to changes in corona current. One disadvantage of the Liebermann detector is its limited sensitivity adjustment.
Another leak detector is disclosed in U.S. Pat. No. 4,282,521 to Liebermann. That detector also senses the concentration of gaseous impurities by applying a high voltage across a pair of electrodes to generate a continuous corona current and by detecting changes in the corona current.
A disadvantage shared by the detectors disclosed in the above patents is that the voltage applied across the electrodes is set and then changes in the concentration of gas are detected by sensing changes in corona current. In order to operate in the continuous corona range, both detectors require that a minimum corona current be maintained. However, since the presence of halogen diminishes the amount of corona current generated by a fixed voltage and since the voltage applied across the electrodes is not controlled or varied, the voltage applied to the electrodes in the above Liebermann detectors must be set unnecessarily high to ensure that the corona current will not be extinguished by an increase in the concentration of halogen gas. The use of an unnecessarily large corona current is a disadvantage because it decreases the life of the sensor electrodes. The use of a large corona current is also a disadvantage in a portable, hand-held leak detector which relies on batteries as its source of power since such a large current wears down the batteries more quickly.
Another halogen gas leak detector is disclosed in U.S. Pat. No. 4,488,118 to Jeffers, et al. That detector also operates by applying a high voltage across a pair of electrodes to generate a continuous corona current and detecting the presence of halogen gas by sensing changes in the corona current. When the Jeffers, et al. detector is turned on, the voltage applied to the electrodes is initially set to a certain value by a relatively complicated digital feedback mechanism, and thereafter the voltage is held constant and the corona current is allowed to vary. Although it might allow the use of a voltage that is lower than that allowed by the Liebermann detectors, the voltage applied by the Jeffers, et al. detector to the electrodes is still too large since the voltage must be set high enough to ensure that subsequent changes in halogen concentration will not cause the corona current to become extinguished, thus resulting in the inoperability of the detector.